It took centuries for the Christian church to come to terms with the concept of human/demon sexual relations.

Oh sure, accusations of "lying with the horned one" are now a staple of medieval witch trial accounts, but as historian Walter Stephens points out in his book "Demon Lovers," the notion of sex between a human being and a bodiless spirit was a "highly complex idea" at the time. The concept stirred up pressing concerns -- both theological and physiological -- that witchcraft theorists struggled with for centuries.

The witchcraft theorists of the 15th and 16th centuries pondered these questions in an attempt to reconcile "confessions" of demonic sex with the metaphysics of their own faith. They compiled thick tomes of pained confessions and continually revised their mythology concerning sorcery.

In their own way, computer scientists continue this work today. Oh, don't fret: Your friendly neighborhood media lab isn't interested in infernal infidelity or Beelzebub booty calls. No, instead they seek to transmit sense data across the Internet and enable interactions with virtual entities and environments.

They're steering us toward a reality previously only dreamt of: sexual congress between the material and immaterial worlds.

Scientists tricked male brown-tailed moths into trying to mate with one another instead of the females. But are sexuality and gender actually fluid concepts in the animal world? Explore animal sexuality, from intersexual clams to homosexual giraffes.

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